A Quite good description I try to give about Reciprocating Pumps. May you get helped.

2. INTRODUCTION
 Pumps are used to increase the energy
level of water by virtue of which it can be
raised to a higher level.
 Reciprocating pumps are positive
displacement pump, i.e. initially, a small
quantity of liquid is taken into a chamber
and is physically displaced and forced
out with pressure by a moving
mechanical elements.
 The use of reciprocating pumps is being
limited these days and being replaced by
centrifugal pumps.

3. INTRODUCTION
 For industrial purposes, they have
become obsolete due to their high
initial and maintenance costs as
compared to centrifugal pumps.
 Small hand operated pumps are still in
use that include well pumps, etc.
 These are also useful where high
heads are required with small
discharge, as oil drilling operations.

4. Main components
 A reciprocation pumps consists of a plunger or a
piston that moves forward and backward inside a
cylinder with the help of a connecting rod and a
crank. The crank is rotated by an external source
of power.
 The cylinder is connected to the sump by a
suction pipe and to the delivery tank by a delivery
pipe.
 At the cylinder ends of these pipes, non-return
valves are provided. A non-return valve allows
the liquid to pass in only one direction.
 Through suction valve, liquid can only be
admitted into the cylinder and through the
delivery valve, liquid can only be discharged into
the delivery pipe.

6. Working of Reciprocating
Pump
 When the piston moves from the left to the
right, a suction pressure is produced in the
cylinder. If the pump is started for the first
time or after a long period, air from the
suction pipe is sucked during the suction
stroke, while the delivery valve is closed.
Liquid rises into the suction pipe by a small
height due to atmospheric pressure on the
sump liquid.
 During the delivery stroke, air in the cylinder
is pushed out into the delivery pipe by the
thrust of the piston, while the suction valve is
closed. When all the air from the suction pipe
has been exhausted, the liquid from the sump
is able to rise and enter the cylinder.

7. Working of Reciprocating
Pump
 During the delivery stroke it is
displaced into the delivery pipe. Thus
the liquid is delivered into the delivery
tank intermittently, i.e. during the
delivery stroke only.

8. Classification of Reciprocating
pumps
Following are the main types of reciprocating pumps:
 According to use of piston sides
◦ Single acting Reciprocating Pump:
If there is only one suction and one delivery pipe
and the liquid is filled only on one side of the
piston, it is called a single-acting reciprocating
pump.
◦ Double acting Reciprocating Pump:
A double-acting reciprocating pump has two
suction and two delivery pipes, Liquid is receiving
on both sides of the piston in the cylinder and is
delivered into the respective delivery pipes.

10. Classification of Reciprocating
pumps
 According to number of cylinder
Reciprocating pumps having more than one cylinder
are called multi-cylinder reciprocating pumps.
◦ Single cylinder pump
◦ Double cylinder pump (or two throw pump)
◦ Triple cylinder pump (three throw pump)
◦ There can be four-cylinder and five cylinder
pumps also, the cranks of which are arranged
accordingly.

12. Discharge through a
Reciprocating Pump
Let
A = cross sectional area of cylinder
r = crank radius
N = rpm of the crank
L = stroke length (2r)
Discharge through pump per second=
Area x stroke length x rpm/60
This will be the discharge when the pump is
single acting.
60
N
LAQth 

13. Discharge through a
Reciprocating Pump
Discharge in case of double acting pump
Discharge/Second =
Where, Ap = Area of cross-section of piston
rod
However, if area of the piston rod is neglected
Discharge/Second =



 

60
)(
60
LNAAALN
Q P
th
60
)2( LNAA
Q P
th


60
2ALN

14. Discharge through a
Reciprocating Pump
 Thus discharge of a double-acting
reciprocating pump is twice than that
of a single-acting pump.
 Owing to leakage losses and time
delay in closing the valves, actual
discharge Qa usually lesser than the
theoretical discharge Qth.

15. Slip
Slip of a reciprocating pump is defined as the
difference between the theoretical and the actual
discharge.
i.e. Slip = Theoretical discharge - Actual
discharge
= Qth. - Qa
Slip can also be expressed in terms of %age and
given by
 10011001
100%
d
th
act
th
actth
C
Q
Q
Q
QQ
slip











16. Slip
Slip Where Cd is known as co-efficient of
discharge and is defined as the ratio of
the actual discharge to the theoretical
discharge.
Cd = Qa / Qth.
Value of Cd when expressed in
percentage is known as volumetric
efficiency of the pump. Its value ranges
between 95---98 %. Percentage slip is of
the order of 2% for pumps in good
conditions.

17. Negative slip
 It is not always that the actual discharge is
lesser than the theoretical discharge. In case
of a reciprocating pump with long suction
pipe, short delivery pipe and running at high
speed, inertia force in the suction pipe
becomes large as compared to the pressure
force on the outside of delivery valve. This
opens the delivery valve even before the
piston has completed its suction stroke. Thus
some of the water is pushed into the delivery
pipe before the delivery stroke is actually
commenced. This way the actual discharge
becomes more than the theoretical
discharge.
 Thus co-efficient of discharge increases from
one and the slip becomes negative.

18. Problem-1: A single-acting reciprocating pump
discharge 0.018 m3 /s of water per second
when running at 60 rpm. Stroke length is 50
cm and the diameter of the piston is 22 cm. If
the total lift is 15 m, determine:
a) Theoretical discharge of the pump
b) Slip and percentage slip of the pump
c) Co-efficient of discharge
d) Power required running the pump
Solution:
L = 0.5 m
Qa = 0.018m3 /s
D = 0.22 m
N = 60 rpm
Hst = 15 m

19. Solution:
(a)
Qth = (π/4)x(0.22)2x(0.5x60/60)
Qth = 0.019 m3 /s
(b) Slip = Qth - Qa
Slip = 0.019 – 0.018
= 0.001 m3 /s
Percentage slip = (Qth - Qa)/ Qth
= (0.019-0.018)/0.019
= 0.0526 or 5.26%
60460
2 LN
D
N
LAQth 








20. Solution:
(c) Cd = Qa / Qth
= 0.018/0.019
= 0.947
(d) Power Input
= ρ g HstQth(Neglecting Losses)
= 1000 x 0.019 x 9.81x 15
= 2796 w or 2.796 kW

21. Comparison of Centrifugal and Reciprocating
Pumps
Centrifugal Pumps Reciprocating Pumps
1. Steady and even flow
2. For large discharge, small heads
3. Can be used for viscous fluids e.g.
oils, muddy water.
4. Low initial cost
5. Can run at high speed. Can be
coupled directly to electric
motor.
6. Low maintenance cost. Periodic
check up sufficient.
7. Compact less floors required.
8. Low head pumps have high
efficiency
9. Uniform torque
10. Simple constructions. Less number
of spare parts needed
1. Intermittent and pulsating flow
2. For small discharge, high heads.
3. Can handle pure water or less
viscous liquids only otherwise
valves give frequent trouble.
4. High initial cost.
5. Low speed. Belt drive necessary.
6. High maintenance cost. Frequent
replacement of parts.
7. Needs 6-7 times area than for
centrifugal pumps.
8. Efficiency of low head pumps as low
as 40 per cent due to the energy
losses.
9. Torque not uniform.
10. Complicated construction. More
number of spare parts needed.

22. Agriculture.
Chemical.
Desalination.
Horizontal Drilling.
General Industries.
Mining.
Oil and Gas.
Pulp and Paper.
Sewer Cleaning.
Steel.